[ale] [OT] Help! burned cd playback wave clipped, original wave perfect

[Ron Frazier (ALE)]

Hi all,

Thanks for the replies to this message.  I know it's been a few days but I wanted to follow up.

Sometimes reality has a way of breaking through any delusions you have about what's going on.

The clipping turned out to be my fault, unknowingly, and it wasn't the cd player.

The audio controls for the mic input on this laptop have two sliders you can move.  One is input level.  And the other is mic boost.  Originally, I had the input level at about 70% and the mic boost at 10 db.  At that point, I was getting good clean waveforms.  Later, I decided I would like it better if the level control was closer to 50%, so I put it there and raised the mic boost control to 20 db.  In that configuration, the waveform is clipped, even though the total level coming into audacity is within bounds.

I don't know why less boost and more level is OK and more boost and less level fails.  I don't know what's going on in the hardware.  I only found this out after I burned another cd from cassette input, which had worked before, and it sounded all muddy and fuzzy.

So, if you're recording in audacity or a similar program, and you get a wave like the bottom one in my picture, you probably have something wrong.

I had to learn several other things too, like how to fix minimal clipping in the source wave, how to boost up weak wave forms ripped from cd, how to reduce down really loud ones from different sources (as I was making a mashup), even how to somewhat remove a dc offset that infected one cassette I had.

Oh, and, if you're creating a cd from an audio book or something, DON'T even think about just recording one hour long track on a cd.  This will drive the person playing the disc crazy, if they want to go to a certain section in the disc and have to hold the fast forward or backward buttons down for 6 minutes to get 45 minutes into the program.

Learned that the hard way too.

In audacity, zoom into the waveform enough so you can see pauses between words or songs.  Add a label at that point.  Then, when you're through editing, you can select the entire thing and select export multiple.  Select to break on labels in the dialog box, set to auto number, and you'll get a number of little track files you can burn to cd.  You may wish to export the full audio for editing later as well.

Also, when I burned the cd, there was an option in the settings that I had to check which said burn without gaps.

For music, I made sure the waveform already had the gaps I wanted, 1 sec before and after each song.  For spoken word audio book, I just let it run.  Having the burning software insert 5 sec gaps in the middle where I didn't want them, the first time, was very frustrating.

I did not try the function that's supposed to automatically break the tracks on silences, but did the breaking myself.

I chose to put 1 hour of stuff on each cd and put track breaks every 6 minutes.

With the help of some stereo equipment that I bartered from Jim Kinney, I was able to eventually create the music disc for my family's event and it worked out very well.

So, thanks to Jim and thanks to you guys for help with the audio.

Sincerely,

Ron



Phil Turmel <philip at turmel.org> wrote:

>Hi Ron,
>
>On 08/29/2013 01:14 AM, Ron Frazier (ALE) wrote:
>
>[trim /]
>
>> Look at this file.
>> 
>> https://dl.dropboxusercontent.com/u/9879631/cd_playback_clipping.png
>> 
>> The top waveform, titled ripped, is the file that was ripped from the
>> cd.  It looks very nice and there is no clipping or excursions beyond
>> the +/- 1 amplitude levels.  It's just like the master file.
>> 
>> The bottom file, titled played, is what was obtained by playing that
>> same file (track) back and rerecording it.  Note that it is severely
>> clipped, BUT, its excursions are nowhere near the +/- 1 limits.  This
>> proves I don't have the input volume too loud.  This is something
>that's
>> happening in the playback circuit of the cd player.  I've confirmed
>the
>> behavior on 2 cd players and observed the same thing on a
>commercially
>> recorded cd.
>> 
>> Also, I've compared the audio playing back the ripped file, versus
>the
>> played file from the cd player.  The ripped version sounds better and
>> fuller.
>> 
>> I wonder if they're doing some dynamic range compression on the
>output
>> of the dac.  Whatever it is, it's not stored in the raw cd data.
>> 
>> Does anyone know what this is and if there is a way to eliminate
>this,
>> so that the true waveform on the cd, which is the same as my master,
>is
>> what comes out of the speakers.
>
>From what is visible in that screenshot, it is almost certainly the CD
>player's output circuit clipping at that output volume level.
>
>Turn the CD player's output volume down until you see no clipping, then
>turn your capture card's input volume up (if necessary) to achieve
>maximum sensitivity for that level.
>
>Clipping can occur in any amplifier circuit between the D/A conversion
>(in the player) and the A/D conversion (in your input card).  If the
>clipping is happening in the player's first analog stages after the D/A
>conversion, before it gets to the volume control, you won't be able to
>fix it.  Your only option would re-level the master WAV to within the
>CD
>player's capabilities.  (I'd toss the CD player if that's true.)
>
>Phil
>
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--

Sent from my Android Acer A500 tablet with bluetooth keyboard and K-9 Mail.
Please excuse my potential brevity if I'm typing on the touch screen.

(PS - If you email me and don't get a quick response, you might want to
call on the phone.  I get about 300 emails per day from alternate energy
mailing lists and such.  I don't always see new email messages very quickly.)

Ron Frazier
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